Method for high voltage power feed on differential cable pairs from a network attached power sourcing device

ABSTRACT

Embodiments of the present invention provide a power feed circuit operable to supply an Ethernet power signal to a coupled Ethernet network. This power feed circuit includes a number of input nodes, differential transistor pairs, active control circuits and output nodes. The input nodes receive a first power signal such as that provided by an isolated 48 volt power supply. Each transistor of the differential transistor pairs couples to one input node. These differential transistor pairs produce a second power signal which may be supplied to the Ethernet network. The active control circuits sense the second power signal passed by each transistor and are operable to apply a feedback signal to the differential transistor pairs based on the sensed power signal. At least one twisted pair couples to each differential transistor pair&#39;s output node and is operable to pass the Ethernet power signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to and incorporatesherein by reference in its entirety for all purposes, U.S. ProvisionalPatent Application No. 60/665,766 entitled “SYSTEMS AND METHODS OPERABLETO ALLOW LOOP POWERING OF NETWORKED DEVICES,” by John R. Camagna, et al.filed on Mar. 28, 2005. This application is related to and incorporatesherein by reference in its entirety for all purposes, U.S. patentapplication Ser. No. 11/207,595 entitled “METHOD FOR HIGH VOLTAGE POWERFEED ON DIFFERENTIAL CABLE PAIRS,” by John R. Camagna, et al. filed Aug.19, 2005; and Ser. No. 11/207,602 entitled “A METHOD FOR DYNAMICINSERTION LOSS CONTROL FOR Ser. No. 10/100/1000 MHZ ETHERNETSIGNALLING,” by John R. Camagna, et al., filed Aug. 19, 2005.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the integration of DC/DCpower conversion within power over Ethernet devices.

BACKGROUND OF THE INVENTION

Many networks such as local and wide area networks (LAN/WAN) structuresare used to carry and distribute data communication signals betweendevices. The various network elements include hubs, switches, routers,and bridges, peripheral devices, such as, but not limited to, printers,data servers, desktop personal computers (PCs), portable PCs andpersonal data assistants (PDAs) equipped with network interface cards.All these devices that connect to the network structure require power inorder to operate. The power of these devices may be supplied by eitheran internal or an external power supply such as batteries or an AC powervia a connection to an electrical outlet.

Some network solutions offer to distribute power over the network inaddition to data communications. The distribution of power over anetwork consolidates power and data communications over a single networkconnection to reduce the costs of installation, ensures power to keynetwork elements in the event of a traditional power failure, andreduces the number of required power cables, AC to DC adapters, and/orAC power supplies which create fire and physical hazards. Additionally,power distributed over a network such as an Ethernet network may providean uninterruptible power supply (UPS) to key components or devices thatnormally would require a dedicated UPS.

Additionally, the growth of network appliances, such as but not limitedto, voice over IP (VoIP) telephones require power. When compared totheir traditional counterparts, these network appliances require anadditional power feed. One drawback of VoIP telephony is that in theevent of a power failure, the ability to contact to emergency servicesvia an independently powered telephone is removed. The ability todistribute power to network appliances or key circuits would allownetwork appliances, such as the VoIP telephone, to operate in a similarfashion to the ordinary analog telephone network currently in use.

The distribution of power over Ethernet network connections is in partgoverned by the IEEE Standard 802.3 and other relevant standards. Thesestandards are incorporated by reference. However, these powerdistribution schemes within a network environment typically requirecumbersome, real estate intensive, magnetic transformers. Additionally,power over Ethernet (PoE) requirements under 802.3 are quite stringentand often limit the allowable power.

There are many limitations associated with using these magnetictransformers. Transformer core saturation can limit the current that canbe sent to a power device. This may further limit the performance of thecommunication channel. The cost and board space associated with thetransformer comprise approximately 10 percent of printed circuit board(PCB) space within a modern switch. Additionally, failures associatedwith transformers often account for a significant number of fieldreturns. The magnetic fields associated with the transformers can resultin lower electromagnetic interference (EMI) performance.

However, magnetic transformers also perform several important functionssuch as providing ground protection, DC isolation and signal transfer innetwork systems. Additionally, integrating devices that perform thesefunctions may give rise to new problems. Thus, there is a need for animproved approach to distributing power in a network environment thataddresses limitations imposed by magnetic transformers while maintainingthe benefits thereof.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a system and methodoperable to provide a power feed on differential cable pairs to networkattached powered devices (PD). This voltage power feed from power sourceequipment (PSE) to PDs substantially addresses the above-identifiedneeds, as well as others. More specifically, various embodiments of thepresent invention provide a PSE network device operable to provide anetwork signal that may include both power and data. This PSE networkdevice includes a network connector and an integrated circuit. Thenetwork connector physically couples the PSE network device to thenetwork. The integrated circuit further includes a power feed circuit.This power feed circuit is operable to combine and pass the receiveddata signals and power signal as a single network signal. A PSEcontroller electrically couples to the integrated circuit but is notnecessarily part of the integrated circuit. The PSE controller isoperable to govern the production and distribution of the power portionof the network signal.

The power feed circuit within embodiments of the present inventionincludes a number of input nodes, differential transistor pairs, activecontrol circuits and output nodes. The input nodes receive a first powersignal such as that provided by an isolated 48 volt power supply. Eachtransistor of the differential transistor pairs couples to one inputnode. These differential transistor pairs produce a second power signalwhich may be supplied to the Ethernet network. The active controlcircuits sense the second power signal passed by each transistor and areoperable to apply a feedback signal to the differential transistor pairsbased on the sensed power signal. At least one twisted pair couples toeach differential transistor pair's output node and is operable to passthe Ethernet power signal

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings wherein:

FIG. 1A depicts current Ethernet network appliances attached to thenetwork and powered separately and their separate power connections;

FIG. 1B depicts various Ethernet network powered devices (PDs) inaccordance with embodiments of the present invention;

FIG. 2A shows a traditional real-estate intensive transformer basedNetwork Interface Card (NIC);

FIG. 2B provides a traditional functional block diagram ofmagnetic-based transformer power supply equipment (PSE);

FIG. 3A provides a functional block diagram of a network powered deviceinterface utilizing non-magnetic transformer and choke circuitry inaccordance with embodiments of the present invention;

FIG. 3B provides a functional block diagram of a PSE utilizingnon-magnetic transformer and choke circuitry in accordance withembodiments of the present invention;

FIG. 4A illustrates two allowed power feeding schemes per the 802.3afstandard;

FIG. 4B illustrates the use of embodiments of the present invention todeliver both the power feeding schemes illustrated with FIG. 4A allowedper the 802.3af standard;

FIG. 5A shows an embodiment of a network powered device (PD) inaccordance with an embodiment of the present invention that integratesdevices at the IC level for improved performance;

FIG. 5B shows an embodiment of a power source equipment (PSE) networkdevice in accordance with an embodiment of the present invention thatintegrates devices at the IC level for improved performance;

FIG. 6A illustrates the technology associated with embodiments of thepresent invention as applied in the case of an enterprise VoIP phone forPD applications;

FIG. 6B illustrates the technology associated with an embodiment of thepresent invention as applied in the case of a network router for PSEapplications;

FIG. 7A provides a block diagram of an IC in accordance with embodimentsof the present invention;

FIG. 7B provides a block diagram of an IC in accordance with embodimentsof the present invention; and

FIGS. 8A-8E illustrate various embodiments of a power feed circuit inaccordance with embodiments of the present invention that are operableto support various data rates and power requirements and multiple cablepairs.

DETAILED DESCRIPTION

Preferred embodiments of the present invention are illustrated in theFIGs., like numerals being used to refer to like and corresponding partsof the various drawings.

The 802.3 Ethernet Standards, which is incorporated herein by reference,allow loop powering of remote Ethernet devices (802.3af). The Power overEthernet (PoE) standard and other like standards intends to standardizethe delivery of power over Ethernet network cables in order to haveremote client devices powered through the network connection. The sideof link that supplies the power is referred to as Powered SupplyEquipment (PSE). The side of link that receives the power is referred toas the Powered device (PD).

Replacing the magnetic transformer of prior systems while maintainingthe functionality of the transformer has been subsumed into theembodiments of the present invention. In order to subsume thefunctionality of the transformer, the circuits provided by embodimentsof the present invention, which may take the form of ICs or discretecomponents, are operable to handle these functions. These functions mayinclude, in the case of an Ethernet network application:

-   -   1) coupling of a maximum of 57V to the IC with the possibility        of 1V peak-peak swing of a 10/100/1000M Ethernet signaling,        (2.8Vp_p for MAU device);    -   2) splitting or combining the signal; 57V DC to the 802.3af        Power Control unit and AC data signal to the PHY (TX and RX),        while meeting the high voltage stress.    -   3) coupling lower voltage (5v and 3.3v) PHY transceiver to high        voltage cable (57V)    -   4) supplying power of 3.3V or 12V through DC-DC peak converter;    -   5) withstanding system-level lighting strikes: indoor lighting        strike (ITU K.41); outdoor lighting strike (IEC 60590)    -   6) withstanding power cross @60 Hz. (IEC 60590)    -   7) fully supporting IEEE 802.3af Specification        Other network protocols may allow different voltage (i.e., a 110        volt circuit coupling to the IC) data rates (i.e., 1 GBPS or        higher), power rating.

In a solid-state implementation, common mode isolation between the earthground of the device and the cable is necessarily required. Fixed commonmode offsets of up to 1500V are possible in traditional systems.Embodiments of the present invention deliver power via cable and theearth ground is used solely for grounding of the device chassis on thePD side. As there is no DC electrical connection between the earth andPoE ground, large voltage offsets are allowable. The PSE side has a dataconnection which may be optically or capacitively isolated. The PSEpower supply is isolated as well.

Second, another transformer function provides surge and voltage spikeprotection from lightning strike and power cross faults. Wires insidethe building comply with the ITU recommendation K.41 for lightningstrikes. Lines external to the building must comply with IEC60950.Lightning strike testing as specified in these Standards consists in acommon mode voltage surge applied between all conductors and the earthor chassis ground. As embodiments of the present invention have no DCconnection to earth ground, minimal stress will occur across the device,thus simplifying the circuits required by embodiments of the presentinvention.

In the case of 802.3.af, power is delivered via the center tap of thetransmit transformer and receive signal transformers for transformerbased designs. The embodiments of the present invention may take up to400 ma DC from the common mode of the signal pair without disturbing theAC (1 MHz-100 MHz) differential signals on the transmit/receive pairs.

FIG. 1A illustrates exemplary devices where power is supplied separatelyto network attached client devices 12-16 that may benefit from receivingpower and data via the network connection. These devices are serviced byLAN switch 10 for data. Additionally, each client device 12-16 hasseparate power connections 18 to electrical outlets 20. FIG. 1Billustrates exemplary devices where switch 10 is a power supplyequipment (PSE) capable power-over Ethernet (PoE) enabled LAN switchthat provides both data and power signals to client devices 12-16. Thenetwork attached devices may include VoIP telephone 12, access points,routers, gateways 14 and/or security cameras 16, as well as other knownnetwork appliances. This eliminates the need for client devices 12-16 tohave separate power connections 18 to electrical outlets 20 as shown inFIG. 1A which are no longer required in FIG. 1B. Eliminating this secondconnection ensures that the network attached device will have greaterreliability when attached to the network with reduced cost andfacilitated deployment.

FIG. 2A provides a typical prior art network interface card 30 for a PDthat includes network connector 32, magnetic transformer 34, EthernetPHY 36, power converter 38, and PD controller 40. Typically, theseelements are all separate and discrete devices. Embodiments of thepresent invention are operable to eliminate the magnetic networktransformer 34 and replace this discrete device with a power feedcircuit. This power feed circuit may be implemented within an integratedcircuit (IC) or as discrete components. Additionally, embodiments of thepresent invention may incorporate other functional specific processors,or any combination thereof into a single IC.

FIG. 2B provides a typical PSE prior art device. Here, power sourcingswitch 50 includes a network connector 32, magnetically coupledtransformer 52, Ethernet physical layer 54, PSE controller 56, andmulti-port switch 58. Typically these elements are all separate anddiscreet devices. Embodiments of the present invention are operable toeliminate the magnetically coupled transformer 52 and replace thistransformer with discreet devices that may be implemented within ICs oras discreet devices.

Although the description herein may focus and describe a system andmethod for coupling high bandwidth data signals and power distributionbetween the IC and cable that uses transformer-less ICs with particulardetail to the 802.3af Ethernet standard, these concepts may be appliedin non-Ethernet applications and non 802.3af applications. Further,these concepts may be applied in subsequent standards that supersede the802.3af standard.

Embodiments of the present invention may provide solid state(non-magnetic) transformer circuits operable to couple high bandwidthdata signals and power signals with new mixed-signal IC technology inorder to eliminate cumbersome, real-estate intensive magnetic-basedtransformers 34 and 52 as pictured in FIGS. 2A and 2B.

Modern communication systems use transformers 34 and 52 to providecommon mode signal blocking, 1500 volt isolation, and AC coupling of thedifferential signature as well as residual lightning or electromagneticshock protection. These functions are replaced by a solid state or otherlike circuits in accordance with embodiments of the present inventionwherein the circuit may couple directly to the line and provide highdifferential impedance and low common mode impedance. High differentialimpedance allows separation of the PHY signal form the power signal. Thelow common mode impedance removes the need for a choke. This allowspower to be tapped from the line. The local ground plane may floatrelative to local earth ground in order to eliminate the need for 1500volt isolation. Additionally through a combination of circuit techniquesand lightning protection circuitry, it is possible to provide voltagespike or lightning protection to the network attached device. Thiseliminates another function performed by transformers in traditionalsystems or arrangements. It should be understood that the technology maybe applied anywhere where transformers are used and should not belimited to Ethernet applications.

Specific embodiments of the present invention may be applied to variouspowered network attached devices or Ethernet network appliances. Suchappliances include, but are not limited to VoIP telephones, routers,printers, and other like devices known to those having skill in the art.Such exemplary devices are illustrated in FIG. 1B.

FIG. 3A is a functional block diagram of a network interface 60 thatincludes network connector 32, non-magnetic transformer and choke powerfeed circuitry 62, network physical layer 36, and power converter 38.Thus, FIG. 3A replaces magnetic transformer 34 with circuitry 62. In thecontext of an Ethernet network interface, network connector 32 may be aRJ45 connector operable to receive a number of twisted pairs. Protectionand conditioning circuitry may be located between network connector 32and non-magnetic transformer and choke power feed circuitry 62 toprovide surge protection in the form of voltage spike protection,lighting protection, external shock protection or other like activefunctions known to those having skill in the art. Conditioning circuitrymay take the form of a diode bridge or other like rectifying circuit.Such a diode bridge may couple to individual conductive lines 1-8contained within the RJ45 connector. These circuits may be discretecomponents or an integrated circuit within non-magnetic transformer andchoke power feed circuitry 62.

In an Ethernet application, the 802.3af standard (PoE standard) providesfor the delivery of power over Ethernet cables to remotely powerdevices. The portion of the connection that receives the power may bereferred to as the powered device (PD). The side of the link thatprovides the power is referred to as the power sourcing equipment (PSE).Two power feed options allowed in the 802.3af standard are depicted inFIG. 4A. In the first alternative, which will be referred to asalternative A, LAN switch 70, which contains PSE 76 feeds power to theEthernet network attached device (PD) 72 along the twisted pair cable 74used for the 10/100 Ethernet signal via the center taps 80 of Ethernettransformers 82. On the line side of the transfer, transformers 84deliver power to PD 78 via conductors 1 and 2 and the center taps 86 andreturn via conductors 3 and 6 and the center taps 86. In the secondalternative, conductors 4, 5, 7 and 8 are used to transmit power withouttransformers. Conductors 4, 5, 7 and 8 remain unused for 10/100 Ethernetdata signal transmissions. FIG. 4B depicts that the network interface ofFIG. 3A and power sourcing switch of FIG. 3B may be used to implementsthese alternatives and their combinations as well.

Returning to FIG. 3A, conductors 1 through 8 of the network connector32, when this connector takes the form of an RJ45 connector, couple tonon-magnetic transformer and choke power feed circuitry 62 regardless ofwhether the first or second alternative provided by 802.3af standard isutilized. These alternatives will be discussed in more detail withreference to FIGS. 4A and 4B. Non-magnetic transformer and choke powerfeed circuitry 62 may utilize the power feed circuit and separates thedata signal portion from the power signal portion. This data signalportion may then be passed to network physical layer 36 while the powersignal is passed to power converter 38.

In the instance where network interface 60 is used to couple the networkattached device or PD to an Ethernet network, network physical layer 36may be operable to implement the 10 Mbps, 100 Mbps, and/or 1 Gbpsphysical layer functions as well as other Ethernet data protocols thatmay arise. The Ethernet PHY 36 may additionally couple to an Ethernetmedia access controller (MAC). The Ethernet PHY 36 and Ethernet MAC whencoupled are operable to implement the hardware layers of an Ethernetprotocol stack. This architecture may also be applied to other networks.Additionally, in the event that a power signal is not received but atraditional, non-power Ethernet signal is received the nonmagnetic powerfeed circuitry 62 will still pass the data signal to the network PHY.

The power signal separated from the network signal within non-magnetictransformer and choke power feed circuit 62 by the power feed circuit isprovided to power converter 38. Typically the power signal received willnot exceed 57 volts SELV (Safety Extra Low Voltage). Typical voltage inan Ethernet application will be 48-volt power. Power converter 38 maythen further transform the power as a DC to DC converter in order toprovide 1.8 to 3.3 volts, or other voltages as may be required by manyEthernet network attached devices.

FIG. 3B is a functional block diagram of a power-sourcing switch 64 thatincludes network connector 32, Ethernet or network physical layer 54,PSE controller 56, multi-port switch 58, and non-magnetic transformerand choke power supply circuitry 66. FIG. 3B is similar to that providedin FIG. 2B, wherein the transformer has been replaced with non-magnetictransformer and choke power supply circuitry 66. This power-sourcingswitch may be used to supply power to network attached devices in placeof the power source equipment disclosed in FIG. 2B.

Network interface 60 and power sourcing switch 64 may be applied to anEthernet application or other network-based applications such as, butnot limited to, a vehicle-based network such as those found in anautomobile, aircraft, mass transit system, or other like vehicle.Examples of specific vehicle-based networks may include a localinterconnect network (LIN), a controller area network (CAN), or a flexray network. All of these may be applied specifically to automotivenetworks for the distribution of power and data within the automobile tovarious monitoring circuits or for the distribution and powering ofentertainment devices, such as entertainment systems, video and audioentertainment systems often found in today's vehicles. Other networksmay include a high speed data network, low speed data network,time-triggered communication on CAN (TTCAN) network, a J1939-compliantnetwork, ISO11898-compliant network, an ISO11519-2-compliant network, aswell as other like networks known to that having skill in the art. Otherembodiments may supply power to network attached devices overalternative networks such as but not limited to a HomePNA local areanetwork and other like networks known to those having skill in the art.The HomePNA uses existing phone wires to share a single networkconnection within a home or building. Alternatively, embodiments of thepresent invention may be applied where network data signals are providedover power lines.

Non-magnetic transformer and choke power feed circuitry 62 and 66eliminate the use of magnetic transformers with integrated systemsolutions that provide the opportunity to increase system density byreplacing magnetic transformers 34 and 52 with solid state power feedcircuitry in the form of an IC or discreet component.

FIG. 5A provides an illustration of an embodiment wherein thenon-magnetic transformer and choke power feed circuitry 62, networkphysical layer 36, power distribution management circuitry 54, and powerconverter 38 are integrated into a single integrated circuit as opposedto being discrete components at the printed circuit board level.Optional protection and power conditioning circuitry 90 may be used tointerface the IC to the network connector.

The Ethernet PHY may support the 10/100/1000 Mbps data rate and otherfuture data networks such as a 10000 Mbps Ethernet network. Thenon-magnetic transformer and choke power feed circuitry 62 will supplythe line power minus the insertion loss directly to the power converter38. This will convert the power first to a 12v supply, then subsequentlyto the lower supply levels. This circuit may be implemented in the 0.18or 0.13 micron process or other like process known to those having skillin the art.

The non-magnetic transformer and choke power feed circuitry 62implements three main functions: 802.3af signaling and load compliance,local unregulated supply generation with surge current protection andsignal transfer between the line and integrated Ethernet PHY. As thedevices are directly connected to the line, the circuit may be requiredto withstand a secondary lightning surge.

In order for the PoE to be 802.3af standard compliant, the PoE may berequired to be able to accept power with either power feeding schemesillustrated in FIGS. 4A and 4B and handle power polarity reversal. Arectifier, such as a diode bridge, or a switching network, may beimplemented to ensure power signals having an appropriate polarity aredelivered to the nodes of the power feed circuit. Any one of theconductors 1, 4, 7 or 3 of the network RJ45 connection can forward biasto deliver current and any one of the return diodes connected canforward bias provide a return current path via one of the remainingconductors. Conductors 2, 5, 8 and 4 are connected in a similar fashion.

The non-magnetic transformer and choke power feed circuitry when appliedto PSE may take the form of a single or multiple port switch in order tosupply power to single or multiple devices attached to the network. FIG.3B provides a functional block diagram of power sourcing switch 64operable to receive power and data signals and then combine these withpower signals, which are then distributed via an attached network. Inthe case where power sourcing switch 64 is a gateway or router, ahigh-speed uplink couples to a network such as an Ethernet network orother like network. This data signal is relayed via network PHY 54 andthen provided to non-magnetic transformer and choke power feed circuitry66. The PSE switch may be attached to an AC power supply or otherinternal or external power supply in order to provide a power signal tobe distributed to network-attached devices that couple to power sourcingswitch 64. Power controller 56 within or coupled to non-magnetictransformer and choke power feed circuitry 66 may determine, inaccordance with IEEE standard 802.3af, whether or not a network-attacheddevice, in the case of an Ethernet network-attached device, is a deviceoperable to receive power from power supply equipment. When it isdetermined in the case of an 802.3af compliant PD is attached to thenetwork, power controller 56 may supply power from power supply tonon-magnetic transformer and choke power feed circuitry 66, which isthen provided to the downstream network-attached device through networkconnectors, which in the case of the Ethernet network may be an RJ45receptacle and cable.

The 802.3af Standard is intended to be fully compliant with all existingnon-line powered Ethernet network systems. As a result, the PSE isrequired to detect via a well defined procedure whether or not the farend is PoE compliant and classify the amount of needed power prior toapplying power to the system. Maximum allowed voltage is 57 volts tostay within the SELV (Safety Extra Low Voltage) limits.

In order to be backward compatible with non-powered systems the DCvoltage applied will begin at a very low voltage and only begin todeliver power after confirmation that a PoE device is present. In theclassification phase, the PSE applies a voltage between 14.5V and 20.5V,measures the current and determines the power class of the device. Inone embodiment the current signature is applied for voltages above 12.5Vand below 23 Volts. Current signature range is 0-44 mA.

The normal powering mode is switched on when the PSE voltage crosses 42Volts. At this point the power MOSFETs are enabled and the large bypasscapacitor begins to charge.

The maintain power signature is applied in the PoE signature block—aminimum of 10 mA and a maximum of 23.5 kohms may be required to beapplied for the PSE to continue to feed power. The maximum currentallowed is limited by the power class of the device (class 0-3 aredefined). For class 0, 12.95 W is the maximum power dissipation allowedand 400 mA is the maximum peak current. Once activated, the PoE willshut down if the applied voltage falls below 30V and disconnect thepower MOSFETs from the line.

The power feed devices in normal power mode provide a differential opencircuit at the Ethernet signal frequencies and a differential short atlower frequencies. The common mode circuit will present the PDcontroller and DC-DC converter load directly to the common mode of theline.

FIG. 6A provides a functional block diagram of a specific networkattached appliance 92. In this case, the network attached appliance is aVoIP telephone. Network connector 32 takes form of an Ethernet networkconnector, such as RJ45 connector, and passes Ethernet signals to powerfeed circuitry 62 and PD controller 40. Non-magnetic transformer andchoke power feed circuitry 62 separates the data signal and powersignal. An optional connection to an external isolated power supplyallows the network attached device to be powered when insufficient poweris available or when more power is required than can be provided overthe Ethernet connection. The data signal is provided to network physicallayer 36. Network physical layer 36 couples to a network MAC to executethe network hardware layer. An application specific processor, such asVoIP processor 94 or related processors, couples to the network MAC.Additionally, the VoIP telephone processors and related circuitry(display 96 and memory 98 and 99) may be powered by power converter 38using power fed and separated from the network signal by non-magnetictransformer and choke power feed circuitry 62. In other embodiments,other network appliances, such as cameras, routers, printers and otherlike devices known to those having skill in the art are envisioned.

FIG. 6B provides a functional block diagram of a specific networkattached PSE device 93. In this embodiment, PSE network device 93 is anEthernet router. Network connector 32 may take the form of Ethernetnetwork connector such as an RJ-45 connector, and is operable todistribute Ethernet signals that include both power and data as combinedby the integrated circuits within PSE 93. PSE 93 includes an integratedcircuit 66 which serves as a nonmagnetic transformer and choke circuit.Various embodiments of the nonmagnetic transformer and choke circuitrywill be discussed in further detail with references to FIGS. 7A-7B and8A-8E.

The 1500 volt isolation between earth ground and the PSE network devicemay be achieved through various means. The data connections may becapacitively isolated, optically isolated or isolated using atransformer. The power connection is isolated using one or more isolatedpower supplies. Capacitors 115, 116 and optocoupler 117 in FIG. 6B areone example of this isolation.

The PSE devices may be a single port or multi-port. As a single portthis device can also be applied to a mid-span application. Data isprovided to Ethernet physical layer 54 either from network devicesattached to network connector 32 or data received from an externalnetwork via internet switch 58 and an uplink. Ethernet switch 58 couldbe an application specific processor or related processors that areoperable to couple PSE 93 via an uplink to an external network.

PSE devices may be integrated into various switches and routers forenterprise switching applications. However, in non-standard networkse.g. automotive etc., these PSE devices may be integrated intocontroller for the attached devices. In the case of multimedia orcontent distribution, these PSE devices may be incorporated into acontroller/set-top box that distributes content and power to attacheddevices.

Nonmagnetic transformer and choke circuitry 66 receives data fromEthernet physical layer 54. Additionally, power is supplied to thenonmagnetic transformer and choke circuitry 66 from isolated powersupply 97. In one embodiment this is a 48-volt power supply. However,this power distribution system may be applied to other powerdistribution systems, such as 110 volt systems as well. PSE controller56 receives the power signal from isolated power supply 97 and isoperable to govern the power signal content within the Ethernet signalsupplied by nonmagnetic transformer and choke circuitry 66. For example,PSE controller 56 may limit the Ethernet power produced by nonmagnetictransformer and choke circuitry 66 based on the requirements of anattached PD. Thus PSE controller 56 is operable to ensure that attachednetwork PDs are not overloaded and are given a proper power signal.Power supply 97 also supplies as shown a power signal to Ethernet PHY54, Ethernet switch 58.

Isolated power supply 97 may be attached to an AC power supply or otherinternal or external power supply in order to provide a power signal tobe distributed to network-attached devices that couple to PSE 93. PSEcontroller 56 may determine, in accordance with IEEE standard 802.3af,whether or not a network-attached device, in the case of anEthernet-attached device, is a device operable to receive power frompower supply equipment. When it is determined that an 802.3af compliantPD is attached to the network, PSE controller 56 may supply power frompower supply 97 to nonmagnetic transformer and choke circuitry 66, whichis then provided to the downstream network-attached device throughnetwork connectors 32.

The 802.3af Standard is intended to be fully compliant with all existingnon-line powered Ethernet systems. As a result, the PSE network deviceis required to detect via a well defined procedure whether or not thefar end network attached device is POE compliant and classify the amountof needed power prior to applying power to the system. Maximum allowedvoltage is 57 volts to stay within the SELV (Safety Extra Low Voltage)limits.

In order to be backward compatible with non-powered systems the DCvoltage applied will begin at a very low voltage and only begin todeliver power after confirmation that a POE device is present. Duringclassification the PSE network device applies a voltage between 14.5Vand 20.5V, and measures the current to determine the power class of thedevice.

The PSE network device enters a normal power supply mode afterdetermining that the PD is ready to receive power. At this point the 48Vsupply is connected to the Ethernet cable. During the normal powersupply mode, a maintain power signature is sensed by the PSE to continuesupplying power. The maximum current allowed is limited by the powerclass of the network attached device.

The power feed devices m1,m2,m3 and m4 shown in FIG. 7A in normal powermode provide a differential open circuit at the Ethernet signalfrequencies and a differential short at lower frequencies. The commonmode circuit will present the capacitive and power management load atfrequencies determined by the gate control circuit.

Additional circuits may be used to implement specific functions inaccordance with various embodiments of the present invention. Variousembodiment of power feed circuits within a PSE are provided in FIGS.7A-7B. FIG. 7A contains a power feed circuit 120 located withinnon-magnetic transformer and choke power feed circuitry 66. The Ethernetnetwork (network) power signal produced complies with alternative A.FIG. 7B depicts a power feed circuit located within non-magnetictransformer and choke power feed circuitry 66 that produces a powersignal that complies with alternative B. Other embodiments are possibleand will be discussed with reference to FIGS. 8A-8D wherein the variousembodiments may comply with alternative A and/or alternative B of802.3af as well as the POE plus standard for higher power applications.The resultant Ethernet signal may be provided via a network connector32, such as the RJ45 connector.

Power is supplied to differential transistor pairs within thenon-magnetic transformer and choke power feed circuitry 66 from powersupply 97. Power supply 97 may couple to the 48 volt node and groundnode within power feed circuit 120 of FIGS. 7A and 7B. Active controlcircuits 125 and 126 may sense the source voltage at the individualtransistors m1 and m2 via circuit pathways 107, 108, 109 and 110respectively. Alternatively, these active control circuits may sense thecurrents passed by the individual transistors. Additionally, activecontrol circuits 125 and 126 may sense the current along line from nodesL1P, L1N, L2P and L2N. This allows the active control circuit 125 and126 to generate control signals 105, 106, 111 and 112 which are appliedto the gates of the transistors. For example, control signals 105 and106 may be applied to the gates of differential transistors M2 and M1respectively. By sensing these voltages or currents, the active controlcircuits may balance the power supplied (current passed) by anyindividual transistor. Comparing the differential voltage seen as thesource of transistors M1 and M2, shown as signals 107 and 108respectively allows active control circuit 125 to adjust the gatecurrents 105 and 106 to balance the current passed by transistors M1 andM2. In other instances, should an open circuit condition result or afailure of an individual transistor or pathway occur, the active controlcircuits may allow the remaining transistor and circuit elements to passa reduced power signal without overloading the remaining circuitelements. Previous solutions would have resulted in an overloadcondition or power delivery shutdown.

Individual power signals are provided on L1P, L1N, L2P, L2N and maycombine with data signals supplied on lines 101, 102, 103 and 104 by PHY128 and 127. The combined Ethernet signal that contains both data andpower is provided over twisted pairs (1, 2) and (3, 6) of the RJ-45connector in accordance with Alternative A on 802.3af standard.

The incoming power signal is provided at the input nodes V48 and Gnd ofactive power control modules 130 and 132. L1N and L1P on the receiveside and on the transmit side L2N and L2P of the power feed circuitprovide the power signal to the network connector. The differentialtransistor pairs are shown as pairs M1 and M2 in active power controlmodule 130 and as M3 and M4 in active power control module 132.Individual Ethernet power signals pass through differential transistorpairs M1 or M2 on the receive side and M3 and M4 on the transmit side.The transistors shown may be MOSFET transistors, bipolar transistors, orother like transistors known to those having skill in the art. The powersignal received from the power supply input nodes pass through senseimpedance such as resistor R1 and R2 on the receive side or R3 and R4 onthe transmit side. The voltage drop across these impedances is used asan input to the active control circuits to balance these circuits.

Active control circuits 125 and 126 may ensure that the power signalspassed through the transistors are of equal magnitude or balanced basedon other criteria. Active control circuits 125 and 126 are operable toprovide common mode suppression, insertion loss control, and currentbalancing by controlling the gate by control signals 105, 106, 111 and112 which are applied to the gates of differential transistors M1, M2,M3 and M4. Additionally, the active control circuits may providetemperature and load control, or other signal conditioning functions.

FIGS. 8A through 8E illustrate various configurations of common modesuppression and active power control circuits that are compliant withAlternative A, Alternative B, and/or POE Plus, and that may supportvarious data rates up to and including gigabyte Ethernet. FIG. 8A showsan embodiment where the upper power feed circuit 120 utilizes a singlepair of active power control circuits 130 and 132 that supply power overtwisted pairs (1, 2) and (3, 6) where twisted pairs (4, 5) and (7, 8)are not used for power and/or data. Thus this first embodiment iscompliant with alternative A. The second embodiment presented in FIG. 8Bis complaint with alternative B where Ethernet data signals are providedon twisted pairs (1, 2) and (3, 6) while power is provided on twistedpairs (4, 5) and (7, 8). Individual twisted pairs in this embodiment areused only to supply power or data but not both.

In FIG. 8C the ability to deliver power over the Ethernet connection isincreased by having the ability to deliver power with additional activepower control modules circuits 134 and 136 over the twisted pairs (4, 5)and (7, 8). It should be noted that power only is provided over twistedpairs (4, 5) and (7, 8). This effectively allows the power supply underAlternative A or Alternative B to be doubled.

FIG. 8D increases the data supply with a PHY 138 operable supportgigabyte Ethernet. In this instance twisted pairs (1, 2) are used tosupply power and data from power supplied by active power control 130.Similarly active power control 132 provides power over twisted pair (3,6). Additionally, in order to support increased data rates (i.e. gigabitEthernet), twisted pairs (1, 2), (3, 6), (4, 5) and (7, 8) all are usedto supply data as well. This involves the addition of common modesuppression circuits 140 and 142 and associated blocking capacitors C2through C9 in order to supply Ethernet data.

FIG. 8E increases both the ability to deliver power and data. This isachieved by supplying power and data on each Ethernet twisted pair.Active power control modules 130, 132, 134 and 136 supply power totwisted pairs (1, 2), (3, 6), (4, 5) and (7, 8) respectively. As shownin FIG. 8D, data is supplied via each twisted pair as previouslydiscussed.

In summary, the embodiments of the present invention provide a powerfeed circuit operable to supplying Ethernet power signal to a coupledEthernet network. This power feed circuit includes a number of inputnodes, differential transistor pairs, active control circuits and outputnodes. The input nodes receive a first power signal such as thatprovided by an isolated 48 volt power supply. Each transistor of thedifferential transistor pairs couples to one input node. Thesedifferential transistor pairs produce a second power signal which may besupplied to the Ethernet network. The active control circuits sense thesecond power signal passed by each transistor and are operable to applya feedback signal to the differential transistor pairs based on thesensed power signal. At least one twisted pair couples to eachdifferential transistor pair's output node and is operable to pass theEthernet power signal.

As one of average skill in the art will appreciate, the term“substantially” or “approximately”, as may be used herein, provides anindustry-accepted tolerance to its corresponding term. Such anindustry-accepted tolerance ranges from less than one percent to twentypercent and corresponds to, but is not limited to, component values,integrated circuit process variations, temperature variations, rise andfall times, and/or thermal noise. As one of average skill in the artwill further appreciate, the term “operably coupled”, as may be usedherein, includes direct coupling and indirect coupling via anothercomponent, element, circuit, or module where, for indirect coupling, theintervening component, element, circuit, or module does not modify theinformation of a signal but may adjust its current level, voltage level,and/or power level. As one of average skill in the art will alsoappreciate, inferred coupling (i.e., where one element is coupled toanother element by inference) includes direct and indirect couplingbetween two elements in the same manner as “operably coupled”. As one ofaverage skill in the art will further appreciate, the term “comparesfavorably”, as may be used herein, indicates that a comparison betweentwo or more elements, items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1.

Although embodiments of the present invention are described in detail,it should be understood that various changes, substitutions andalterations can be made hereto without departing from the spirit andscope of the invention.

1. A power feed circuit within a network attached power sourcing device,wherein the power feed circuit is operable to supply an Ethernet powersignal to a coupled Ethernet network, comprising: a plurality of inputnodes operable to receive a first power signal; a plurality ofdifferential transistor pairs wherein each transistor of thedifferential transistor pairs electrically couples to one input node,wherein the differential transistor pairs are operable to produce asecond power signal; active control circuit(s) operable to sense thesecond power signal passed by each transistor, and wherein the activecontrol circuit(s) are operable to apply a feedback signal to thedifferential transistor pairs; and at least one twisted pair coupled toeach differential transistor pair, wherein the twisted pair couples to anetwork connector, and wherein the twisted pairs are operable to passthe Ethernet power signal.
 2. The power feed circuit of claim 1, furthercomprising two pairs of impedance sense resistors, wherein eachimpedance sense resistor is coupled to one input node and one transistorof the differential transistor pairs, wherein each impedance senseresistors is operable to pass a current supplied by the coupled inputnode.
 3. The power feed circuit of claim 1, wherein the active controlcircuit(s) further comprise an amplifier coupled to the drains of eachtransistor within a differential transistor pair, wherein the amplifierare operable to: amplify a differential voltage across the pair ofimpedance sense resistors coupled to the differential transistor pair;and apply a feedback signal to a gate of each transistor within thedifferential transistor pair coupled to the amplifier, wherein thefeedback signal is based on the differential voltage, wherein thefeedback signal forces the Ethernet power signal passed by eachtransistor in the differential transistor pair to be equal.
 4. The powerfeed circuit of claim 1, further comprising combining circuitry operableto combine a data signal with the Ethernet power signal.
 5. The powerfeed circuit of claim 1, wherein the network connector comprises an RJ45connector operable to physically couple the network attached powersourcing device to the Ethernet network, and wherein the RJ45 connectorcouples to twisted pairs that further comprise conductors 1 and 2; 3 and6; 4 and 5; and 7 and 8; and the Ethernet power signal utilizingconductors 1, 2, 3, and 6, and/or conductors 4, 5, 7, and
 8. 6. Thepower feed circuit of claim 1, wherein the power feed circuit isimplemented as an integrated circuit (IC).
 7. The power feed circuit ofclaim 6, wherein the integrated circuit (IC) further comprises: anEthernet physical layer (PHY) module; an Ethernet media accesscontroller (MAC) wherein the Ethernet PHY module and Ethernet MAC areoperable to implement hardware layers of an Ethernet network protocolstack; a power management module; and Ethernet network PD applicationspecific processors and memory.
 8. The power feed circuit of claim 7,wherein the Ethernet power signal is operable to at least partiallypower an Ethernet network powered device (PD).
 9. The power feed circuitof claim 1, wherein the input nodes couple to an isolated power supply.10. The power feed circuit of claim 9, wherein the isolated power supplycomprises a 48 volt power supply.
 11. The power feed circuit of claim 1,further comprising an Ethernet PHY module operable to implement physicallayer functions associated with data rates selected from the group ofdata rates consisting of: 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps. 12.The power feed circuit of claim 11, wherein the network attached powersourcing device further comprises a multi-port switch operable to couplethe Ethernet PHY module to an external network.
 13. A method operable toproduce an Ethernet power signal within a power source equipment (PSE)network device, comprising: physically coupling a plurality of inputnodes within the PSE network device to an isolated power supply; drawingcurrents from the plurality of input nodes through differentialtransistor pairs; sensing individual currents drawn through eachtransistor of the differential transistor pairs; comparing theindividual currents drawn through each transistor of the differentialtransistor pairs; generating feedback signals based on the comparison ofthe individual currents drawn through each transistor of thedifferential transistor pairs; and applying the feedback signals to thedifferential transistor pairs; and supplying the currents drawn throughthe differential transistor pairs to a network attached power device(PD) via an Ethernet network.
 14. The method of claim 13, whereinsensing individual currents drawn through each transistor of thedifferential transistor pairs further comprises sensing voltage dropsacross impedance sense resistors, wherein each impedance sense resistoris coupled to one input node and one transistor of the differentialtransistor pairs.
 15. The method of claim 13, wherein the feedbacksignal applied to the differential transistor pair balances the currentspassed by each transistor of the differential transistor pair.
 16. Themethod of claim 13, further comprising combining a data signal with theEthernet power signal.
 17. The method of claim 13, wherein supplying thecurrents drawn through the differential transistor pairs to a networkattached power device (PD) further comprises: supplying the currents toa network connector, wherein twisted pairs coupled the network connectorand couple the PSE network device to the network attached PD.
 18. Themethod of claim 13, wherein the twisted pairs further compriseconductors 1 and 2; 3 and 6; 4 and 5; and 7 and 8; and the Ethernetpower signal utilizes conductors 1, 2, 3, and 6, and/or conductors 4, 5,7, and
 8. 19. A method operable to produce an Ethernet power signalwithin a power source equipment (PSE) Ethernet network device,comprising: physically coupling a plurality of input nodes within thePSE network device to an isolated power supply; drawing currents fromthe plurality of input nodes through differential transistor pairs;sensing individual currents drawn through each transistor of thedifferential transistor pairs; producing control signals for of eachtransistor within the differential transistor pair based on theindividual currents drawn through each transistor of the differentialtransistor pairs; applying the control signal to a gate of eachtransistor, wherein the control signal forces the current passed by eachtransistor in a differential transistor pair to be equal; and supplyingthe currents drawn through the differential transistor pairs to anetwork attached power device (PD) via an Ethernet network.
 20. Themethod of claim 18, further comprising: physically coupling an Ethernetnetwork PD to the Ethernet network.
 21. The method of claim 20, wherein:RJ45 connectors physically couple the PSE Ethernet network device to theEthernet network, and wherein the RJ45 connector couples to twistedpairs that further comprise conductors 1 and 2; 3 and 6; 4 and 5; and 7and 8.